1. Field of the Invention
The instant invention relates to methods of and apparatus for insulating buildings. More particularly, the instant invention relates to methods of and apparatus for insulating buildings, wherein the skeletal structure of buildings is insulated to prevent heat transfer either into or out of the buildings.
2. Technical Considerations and Prior Art
Metal buildings necessarily have high heat transfer rates through their metallic walls and roofs. Consequently, it is necessary to extensively insulate metal buildings, so as to prevent excessive heat transfer. In warm climates, considerable energy is necessary to cool these buildings, and in cooler climates considerable energy is necessary to heat these buildings. In order for metal buildings to be economically utilized with their concomitant advantages, it is continuously necessary to devise ways to limit energy consumption.
In metal buildings a great deal of energy is lost through the roof due to exposed metal purlins which support panels forming the roof. These purlins extend down into the building and, in effect, turn the building into a finned heat exchanger, in which the interior surface of the roof is greatly increased by the surface area of the purlins. This increased surface area due to the purlins increases the area over which both radiant and convective heat transfer takes place between the environment within the building and the purlins. In a cool climate, where the environment in the building is maintained warmer than the atmosphere, the purlins conduct heat transferred thereto out into the atmosphere. In a warm climate, where the environment of the building is maintained cooler than the atmosphere, the purlins conduct heat into the building and, by both radiation and convection, transfer the heat to the environment within the building.
The prior art, while concerned with reducing heat transfer from metal buildings to the atmosphere, has failed to recognize the aforementioned analogy between a building and a finned heat exchanger and, therefore, has not corrected the problem. In the prior art, insulation has been placed on top of the purlins, underneath the purlins and between the purlins. Generally, the purlins are Z-shaped with a main web portion and top and bottom flange portions which project in opposite directions from the web portion. In placing the insulation between the purlins, the bottom flange portion is, in the prior art, always left exposed, so that heat is readily conducted from the bottom flange through the web to the roof structure and into the atmosphere.